Organic light emitting diode display panel and method of manufacturing the same

ABSTRACT

A method of manufacturing an organic light emitting diode display panel, including forming a lower substrate, the lower substrate including a first area and a second area; forming an organic light emitting device on the lower substrate; disposing a polymer network liquid crystal on the organic light emitting device; forming a second optical layer in the second area, the second optical layer including the polymer network liquid crystal; and varying an optical property of the polymer network liquid crystal so as to form a first optical layer in the first area. The optical property of the polymer network liquid crystal in the first optical layer differs from the optical property of the polymer network liquid crystal in the second optical layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No.14/447,160, filed on Jul. 30, 2014, and claims priority from and thebenefit of Korean Patent Application No. 10-2014-0001310, filed on Jan.6, 2014, which is hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND

Field

Exemplary embodiments of the present invention relate to an organiclight emitting diode display panel, and a method of manufacturing thesame.

Discussion of the Background

In general, an organic light emitting diode display panel includes adisplay panel including pixels, and a driver to control the displaypanel. Each pixel includes an organic light emitting device. The organiclight emitting device includes an organic light emitting layer to emitlight, and electrodes to apply driving voltages to the organic lightemitting layer.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Exemplary embodiments of the present invention provide an organic lightemitting diode display panel having improved light transmissionefficiency.

Exemplary embodiments of the present invention also provide a method ofmanufacturing the organic light emitting diode display panel.

Additional features of the invention will be set forth in thedescription which follows, and in part will become apparent from thedescription, or may be learned from practice of the invention.

An exemplary embodiment of the present invention discloses an organiclight emitting diode display panel including an upper substrate, anorganic light emitting device facing the upper substrate and emittinglight to the upper substrate, and a light extraction layer disposedbetween the upper substrate and the organic light emitting device. Thelight extraction layer includes first and second optical layers, eachhaving a polymer network liquid crystal and each having differentoptical properties, and the light extraction layer exits the light tothe outside of the upper substrate. The optical property of the polymernetwork liquid crystal in the first optical layer is different from theoptical property of the polymer network liquid crystal in the secondoptical layer.

An exemplary embodiment of the present invention also discloses a methodof manufacturing an organic light emitting diode display panel,including forming a lower substrate including a first area and a secondarea, forming an organic light emitting device on the lower substrate,providing a polymer network liquid crystal on the organic light emittingdevice, forming a second optical layer including the polymer networkliquid crystal in the second area, and processing the polymer networkliquid crystal such that an optical property of the polymer networkliquid crystal is varied to form a first optical layer in the firstarea.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1 is a block diagram illustrating an organic light emitting diodedisplay device according to an exemplary embodiment of the presentinvention.

FIG. 2 is an equivalent circuit diagram of a pixel shown in FIG. 1.

FIG. 3 is a cross-sectional view of a display panel shown in FIG. 1.

FIG. 4 is a view illustrating a polymer network liquid crystal.

FIG. 5 is a view illustrating a method of manufacturing a shearedpolymer network liquid crystal.

FIG. 6 is a cross-sectional view of a display panel according to anotherexemplary embodiment of the present invention.

FIG. 7 is a view illustrating a method of manufacturing an alignedpolymer network liquid crystal.

FIG. 8 is a graph illustrating transmittance and haze of the polymernetwork liquid crystal according to an electric field applied to thepolymer network liquid crystal.

FIG. 9 is a cross-sectional view of a display panel according to anotherexemplary embodiment of the present invention.

FIG. 10 is a cross-sectional view of a display panel according toanother exemplary embodiment of the present invention.

FIG. 11 is a graph illustrating a simulation result of a colorcoordinate variation as a function of a viewing angle illustrating acomparison example and a display panel according to an exemplaryembodiment of the present invention.

FIGS. 12A, 12B, 12C, 12D, and 12E are cross-sectional views illustratinga method of manufacturing a display panel according to an exemplaryembodiment of the present invention.

FIGS. 13A and 13B are cross-sectional views illustrating a method ofmanufacturing a display panel according to another exemplary embodimentof the present invention.

FIGS. 14A, 14B, and 14C are cross-sectional views illustrating portionsof a method of manufacturing a display panel according to anotherexemplary embodiment of the present invention.

FIGS. 15A and 15B are cross-sectional views illustrating a method ofmanufacturing a display panel according to another exemplary embodimentof the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of elements may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to”, or “coupled to” another element or layer, itcan be directly on, connected, or coupled to the other element or layer,or intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”,or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items. It willbe understood that for the purposes of this disclosure, “at least one ofX, Y, and Z” can be construed as X only, Y only, Z only, or anycombination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

Referring to FIG. 1, the organic light emitting diode display device1000 includes a display panel 400 to display an image, a gate driver 200and a data driver 300 to drive the display panel 400, and a timingcontroller 100 to control the gate driver 200 and the data driver 300.

The timing controller 100 receives image signals RGB and control signalsCS from the outside of the organic light emitting diode display device1000. The timing controller 100 converts a data format of the imagesignals RGB into a data format appropriate to an interface between thedata driver 300 and the timing controller 100 to generate image dataDATA, and transmits the image data DATA to the data driver 300. Inaddition, the timing controller 100 generates a data control signal DCS,e.g., an output start signal, a horizontal start signal, etc., and agate control signal GCS, e.g., a vertical start signal, a vertical clocksignal, a vertical clock bar signal, etc., on the basis of the controlsignals CS. The data control signal DCS is transmitted to the datadriver 300 and the gate control signal GCS is transmitted to the gatedriver 200.

The gate driver 200 sequentially outputs gate signals in response to thegate control signal GCS provided from the timing controller 100.

The data driver 300 converts the image data DATA into data voltages inresponse to the data control signal DCS provided from the timingcontroller 100, and applies the image data DATA to the display panel400.

The display panel 400 includes gate lines GL1 to GLn, data lines DL1 toDLm, and pixels PX11 to PXnm. The pixels PX11 to PXnm are each connectedto a corresponding gate line of the gate lines GL1 to GLn and acorresponding data line of the data lines DL1 to DLm.

The gate lines GL1 to GLn extend in a first direction D1 and arearranged in a second direction D2 crossing the first direction D1. Thedata lines DL1 to DLm are insulated from the gate lines GL1 to GLn whilecrossing the gate lines GL1 to GLn. The data lines DL1 to DLm extend inthe second direction D2, and are arranged in the first direction D1.

The display panel 400 receives a first source voltage ELVDD and a secondsource voltage ELVSS. Each of the pixels PX11 to PXnm is turned on inresponse to a corresponding one of the gate signals. Each of the pixelsPX11 to PXnm receives the first source voltage ELVDD and the secondsource voltage ELVSS, and generates a light in response to acorresponding one of the data signals. The first source voltage ELVDD ishigher than the second source voltage ELVSS.

Each of the pixels PX11 to PXnm includes at least one transistor, atleast one capacitor, and an organic light emitting device.

FIG. 2 is an equivalent circuit diagram of a pixel PXij connected to ani-th gate line GLi of the gate lines GL1 to GLn, and a j-th data lineDLj of the data lines DL1 to DLm. The pixel PXij includes a firsttransistor TR1, a second transistor TR2, a capacitor Cap, and an organiclight emitting device OL. The first transistor TR1 includes a first gateelectrode GE1 connected to the i-th gate line GLi, a first sourceelectrode SE1 connected to the j-th data line DLj, and a first drainelectrode DE1. The first transistor TR1 outputs the data signal appliedto the j-th data line DLj in response to the gate signal applied to thei-th gate line.

The capacitor Cap includes a first electrode connected to the firsttransistor TR1 and a second electrode that is supplied with the firstsource voltage ELVDD. The capacitor Cap is charged with electric chargescorresponding to a difference between the voltage corresponding to thedata signal from the first transistor TR1 and the first source voltageELVDD.

The second transistor TR2 includes a second gate electrode GE2 connectedto the first drain electrode DE1 of the first transistor TR1 and thefirst electrode of the capacitor Cap, a source electrode SE2 that issupplied with the first source voltage ELVDD, and a second drainelectrode DE2. The second drain electrode DE2 is connected to theorganic light emitting device OL.

The second transistor TR2 controls a driving current flowing through theorganic light emitting device OL in response to an amount of electriccharge charged in the capacitor Cap. A turn-on period of the secondtransistor TR2 is determined by the amount of the electric chargecharged in the capacitor Cap. The second transistor TR2 applies avoltage having a level lower than that of the first source voltage ELVDDto the organic light emitting device OL.

The organic light emitting device OL emits light during the turn-onperiod of the second transistor TR2. The light emitted from the organiclight emitting device OL has a color determined depending on thematerial of the organic light emitting device OL. For instance, thecolor of the light emitted from the organic light emitting device OL maybe red, green, blue, or white.

FIG. 3 is a cross-section of the pixel PXij and the display panel 400.

The display panel 400 includes a lower substrate 410, an upper substrate420 facing the lower substrate 410, and a light extraction layer 430.The display panel 400 includes a display area DA and a non-display areaNDA. The upper substrate 420 includes an upper base substrate 423, acolor filter 422, and a black matrix 421.

The upper base substrate 423 serves as a base for the upper substrate420 and includes a glass or plastic material having high lighttransmittance.

The color filter 422 is disposed at a position corresponding to thedisplay area DA. The color filter 422 may be a red, green, or blue colorfilter.

The black matrix 421 is disposed at a position corresponding to thenon-display area NDA, and blocks light traveling thereto. The blackmatrix 421 includes a light blocking material to block light.

The lower substrate 410 includes a lower base substrate 411, aninsulating layer 412, a pixel definition layer 413, the secondtransistor TR2, and the organic light emitting device OL. The lower basesubstrate 411 serves as a base for the lower substrate 410, and includesa glass or plastic material having high light transmittance.

The second transistor TR2 is disposed on the lower base substrate 411,and further includes a gate insulating layer GI and a semiconductorlayer AL.

The second gate electrode GE2 is disposed on the lower base substrate411. The semiconductor layer AL is disposed on the second gate electrodeGE2, while the gate insulating layer GI is disposed between thesemiconductor layer AL and the second gate electrode GE2. The gateinsulating layer GI electrically insulates the semiconductor layer ALfrom the second gate electrode GE2. The second source electrode SE2makes contact with the semiconductor layer AL, and the second drainelectrode DE is spaced apart from the second source electrode SE2 andmakes contact with the semiconductor layer AL.

An insulating layer 412 is disposed on the second transistor TR2. Theinsulating layer 412 includes an inorganic and/or an organic material. Acontact hole is formed in the insulating layer 412 to expose a portionof the second drain electrode DE2.

The organic light emitting device OL includes a first electrode OE1, asecond electrode OE2, and a light emitting layer EL. The first electrodeOE1 is disposed on the insulating layer 412, and is electricallyconnected to the second drain electrode DE2 through the contact hole.

The pixel definition layer 413 is disposed on the lower base substrate411 to correspond to the non-display area NDA. The pixel definitionlayer 413 covers a portion of the first electrode OE1 disposed in thenon-display area NDA. An opening is formed in the pixel definition layer413 to expose at least a portion of the first electrode OE1. The firstelectrode OE1 receives the first source voltage ELVDD from the seconddrain electrode DE2.

The light emitting layer EL is disposed on at least a portion of thepixel definition layer 413 and the first electrode OE1. The lightemitting layer EL makes contact with the first electrode OE1 through theopening. The light emitting layer EL may be formed of various luminoussubstances containing a host and a dopant. A fluorescent dopant and aphosphorescent dopant may be used as the dopant. As the host, forexample, Alq3C CBP(4,4′-N,N′-dicarbazole-biphenyl) may be used, but itshould not be limited thereto or thereby.

The second electrode OE2 is disposed over the light emitting layer ELand the pixel definition layer 413. The second electrode OE2 covers thelight emitting layer EL and contacts the light emitting layer EL. Thesecond electrode OE2 receives the second source voltage ELVSS.

An electric field corresponding to a difference in electric potentialbetween the first source voltage ELVDD and the second source voltageELVSS is formed in the light emitting layer EL. The light emitting layerEL emits light to the upper substrate 420 in response to the electricfield.

The light extraction layer 430 is disposed between the upper substrate420 and the second electrode OE2. The light extraction layer 430includes a first optical layer 431 and a second optical layer 432, anddirects light towards the upper substrate 420 through the first andsecond optical layers 431 and 432.

The first light optical layer 431 includes a polymer network liquid PNLC(refer to FIG. 4), and the second light optical layer 432 includes asheared polymer network liquid crystal S-PNLC (refer to FIG. 5).

Hereinafter, the polymer network liquid crystal PNLC and the shearedpolymer network liquid crystal S-PNLC will be described in detail withreference to FIGS. 4 and 5.

FIG. 4 is a view showing the polymer network liquid crystal and FIG. 5is a view showing a method of manufacturing the sheared polymer networkliquid crystal.

Referring to FIG. 4, the polymer network liquid crystal PNLC includespolymers PM and liquid crystals LM. The polymers PM are distributedbetween the liquid crystals LM in a network arrangement.

The sheared polymer network liquid crystal S-PNLC is formed by radiatingan ultraviolet ray UV toward the polymer network liquid crystal PNLC andcuring the polymers PM. In more detail, each polymer PM cross-links withan adjacent polymer PM thereto in response to the intensity of theultraviolet ray UV. This is referred to as a “cross-linking” or a“curing” reaction.

The sheared polymer network liquid crystal S-PNLC has a refractive indexthat is proportional to the degree of cross-linking. For instance, whena refractive index of the polymers PM is large, the refractive index ofthe sheared polymer network liquid crystal S-PNLC becomes larger as thedegree of the cross-linking becomes higher. The refractive index of thesheared polymer network liquid crystal S-PNLC is greater than therefractive index of the polymer network liquid crystal PNLC.

Referring to FIG. 3, the second optical layer 432 has a lens structure,e.g., which may be, but is not limited to, a convex lens structure.

The display panel 400 includes a first area OA1 including the displayarea DA, and a second area OA2 surrounding the first area OA1. Thesecond optical layer 432 may be disposed on the second electrode OE2 tocorrespond to the first area OA1, but the location of the second opticallayer 432 need not be so limited. That is, the locations of the firstarea OA1 and the second optical layer 432 may vary with respect to thedisplay area DA and the non-display area NDA. For instance, the firstarea OA1 may be defined inside the display area DA. Accordingly, thesecond optical layer 432 may be provided only in the display area DA. Inaddition, the first area OA1 may be defined to match the display areaDA. Therefore, a boundary of the display area DA may match a boundary ofthe convex lens structure of the second optical layer 432.

The first optical layer 431 is disposed at a position adjacent to andsurrounding the second optical layer 432. In more detail, the firstoptical layer 431 is disposed between the second electrode OE2 and theupper substrate 420 to correspond to the second area OA2. In addition,the first optical layer 431 is disposed between an upper surface of theconvex lens structure of the second optical layer 432 and the uppersubstrate 420 in the first area OA1. Thus, a boundary surface betweenthe first optical layer 431 and the second optical layer 432 has aconvex surface toward the upper substrate 420 to correspond to theconvex lens structure.

A first refractive index of the first optical layer 431 differs from asecond refractive index of the second optical layer 432. The first andsecond optical layers 431 and 432 include the polymer network liquidcrystal PNLC and the sheared polymer network liquid crystal S-PNLC,respectively, and the sheared polymer network liquid crystal S-PNLC hasa refractive index greater than that of the polymer network liquidcrystal PNLC. Accordingly, the second refractive index is greater thanthe first refractive index, and the difference is in a range of about1.4 to about 2.

The light emitted from the organic light emitting device OL travels invarious directions. Of all the light emitted from the organic lightemitting device OL, a side surface light SL traveling to the blackmatrix 421 is blocked by the black matrix 421, thereby reducing thelight transmission efficiency of the display panel 400. According to thepresent exemplary embodiment, however, because the second optical layer432 has the convex lens structure, and the second refractive index isgreater than the first refractive index, the light extraction layer 430changes an optical path of the side surface light SL such that the sidesurface light SL travels to the upper substrate 420 corresponding to thedisplay area DA and exits to the outside of the upper substrate 420through the upper substrate 420. In other words, the light extractionlayer 430 condenses the light, which travels to the side surface amongthe light emitted from the organic light emitting device OL, to thedisplay area DA using the convex lens structure, thereby improving thelight transmission efficiency of the display panel 400.

In more detail, the side surface light SL is emitted from the organiclight emitting device OL and travels toward the black matrix 421 along adirection inclined to the first direction D1. When the side surfacelight SL reaches the boundary surface between the first and secondoptical layers 431 and 432, the side surface light SL is refracted bythe boundary surface, and thus, the side surface light SL exits to theoutside of the upper substrate 420 corresponding to the display area DAthrough the upper substrate 420.

In addition, the emitted light includes a front surface light FLtraveling to the upper substrate 420 corresponding to the display areaDA. The side surface light SL has a first set of color coordinates, andthe front surface light FL has a second set of color coordinatesdifferent from the set of first color coordinates. Accordingly, thecolor coordinates of the light may vary depending on a viewing angle.However, according to the present exemplary embodiment, the optical pathof the side surface light SL is changed by the light extraction layer430, so that the side surface light SL exits to the outside through theupper substrate 420 corresponding to the display area DA together withthe front surface light FL. Therefore, the light obtained by mixing theside surface light SL and the front surface light FL is perceived by auser. Thus, variations of the color coordinates may be reducedregardless of the viewing angle.

FIG. 6 is a cross-sectional view showing a display panel 401 accordingto another exemplary embodiment of the present disclosure. In FIG. 6,the same reference numerals denote the same elements in FIGS. 1 to 5,and thus, detailed descriptions of the same elements will be omitted.

Referring to FIG. 6, the display panel 401 includes a light extractionlayer 440. The display panel 401 has the same structure and function asthose of the display panel 400 shown in FIG. 3 except for the lightextraction layer 440.

The light extraction layer 440 is disposed between the upper substrate420 and the second electrode OE2. The light extraction layer 440includes a first optical layer 441 and a second optical layer 442, andoutputs light emitted from the organic light emitting device OL towardsthe upper substrate 420 through the first and second optical layers 441and 442.

The first optical layer 441 includes an aligned polymer network liquidcrystal O-PNLC (refer to FIG. 7), and the second optical layer 442includes the sheared polymer network liquid crystal S-PNLC.

Hereinafter, the aligned polymer network liquid crystal O-PNLC will bedescribed in detail with reference to FIGS. 7 and 8.

FIG. 7 is a view illustrating a method of manufacturing the alignedpolymer network liquid crystal, and FIG. 8 is a graph showingtransmittance and the degree of haze of the polymer network liquidcrystal according to an electric field applied to the polymer networkliquid crystal.

The aligned polymer network liquid crystal O-PNLC is formed by applyingan electric field EF to the polymer network liquid crystal PNLC to alignthe polymers PM and the liquid crystals LM, and radiating theultraviolet ray UV to the polymer network liquid crystal PNLC to curethe polymers PM while the polymers PM and the liquid crystals LM arealigned. In more detail, when the electric field EF is applied in athickness direction of the polymer network liquid crystal PNLC, thepolymers PM and the liquid crystals LC are aligned in the thicknessdirection in response to the electric field. Then, when the ultravioletray UV is radiated to the polymer network liquid crystal PNLC, thepolymers PM are cross-linked to each other.

The aligned polymer network liquid crystal O-PNLC has a degree of hazedetermined according to the intensity of the electric field EF appliedto align the polymers PM and the liquid crystals LM. In detail, as shownin FIG. 8, as the intensity of the electric field EF becomes greater,the transmittance of the polymer network liquid crystal O-PNLC becomeslarger, and the degree of haze of the aligned polymer network liquidcrystal O-PNLC becomes smaller. Therefore, when the intensity of theelectric field EF becomes stronger, the transmittance OT of the alignedpolymer network liquid crystal O-PNLC is about 80% and the degree ofhaze OH of the aligned polymer network liquid crystal O-PNLC is about10%. Thus, the aligned polymer network liquid crystal O-PNLC transmitsthe light incident thereto without scattering the light.

On the contrary, when the intensity of the electric field EF becomesweaker, the transmittance OT of the aligned polymer network liquidcrystal O-PNLC is about 30% and the degree of haze OH of the alignedpolymer network liquid crystal O-PNLC is about 65%, and thus the alignedpolymer network liquid crystal O-PNLC scatters the light incidentthereto.

Referring to FIG. 6, the display panel 401 includes a first area OA1 anda second area OA2 surrounding the first area OA1. The first area OA1 andthe second area OA2 are sequentially arranged in the first direction D1.

The first optical layer 441 is disposed between the second electrode OE2and the upper substrate 420 to correspond to the first area OA1, and thesecond optical layer 442 is disposed between the second electrode OE2and the upper substrate 420 to correspond to the second area OA2.Accordingly, a boundary surface between the first and second areas OA1and OA2 is formed along the third direction D3.

The arrangement of the first area OA1 and the first optical layer 441corresponding to the first area OA1 may vary with respect to the displayarea DA and the non-display area NDA. For instance, the first area OA1may be defined inside the display area DA. Accordingly, the firstoptical layer 441 may be provided only in the display area DA.

In addition, the first area OA1 may be defined to match the display areaDA. Therefore, a boundary of the display area DA may match the boundaryof the convex lens structure of the second optical layer 442.

The first optical layer 441 has a first degree of haze and the secondoptical layer 442 has a second degree of haze different from the firstdegree of haze. Because the first optical layer 441 and the secondoptical layer 442 respectively include the aligned polymer networkliquid crystal O-PNLC and the sheared polymer network liquid crystalS-PNLC, and the aligned polymer network liquid crystal O-PNLC has asmaller degree of haze than that of the sheared polymer network liquidcrystal S-PNLC, the first degree of haze is less than the second degreeof haze.

In addition, the first optical layer 441 has a first transmittance, andthe second optical layer 442 has a second transmittance different fromthe first transmittance. The first degree of haze is less than thesecond degree of haze, and therefore, the first transmittance is greaterthan the second transmittance.

The light emitted from the organic light emitting device OL travels invarious directions. In particular, a portion of the side surface lightSL emitted inclined to a line normal to the upper surface of the lowerbase substrate 410 travels to the black matrix 421 and is blocked andabsorbed by the black matrix 421. In this case, the light transmissionefficiency of the display panel 401 is reduced. However, according tothe present exemplary embodiment, the second optical layer 442 has adegree of haze that is greater than that of the first optical layer 441,and is disposed under the black matrix 421. Accordingly, the secondoptical layer 442 scatters the light before the light is incident to theblack matrix 421 to allow the portion of the side surface light SL toexit to the display area DA. Therefore, the amount of the light blockedand absorbed by the black matrix 421 is reduced, and the lighttransmission efficiency of the display panel 421 is improved.

In addition, the optical path of the side surface light SL having thefirst set of color coordinates is changed by the second optical layer442, and the side surface light SL exits to the outside through theupper substrate 420 corresponding to the display area DA together withthe front surface light FL having the second set of color coordinates.Thus, the light obtained by mixing the side surface light SL and thefront surface light FL, which have different sets of color coordinates,is perceived by the user, and thus, variations of the color coordinatesmay be reduced regardless of the viewing angle.

FIG. 9 is a cross-sectional view showing a display panel 402 accordingto another exemplary embodiment of the present invention. In FIG. 9, thesame reference numerals denote the same elements in FIGS. 1 to 8, andthus, detailed descriptions of the same elements will be omitted.

Referring to FIG. 9, the display panel 402 includes a light extractionlayer 450. The display panel 402 has the same structure and function asthose of the display panel 401, except for the light extraction layer450.

The light extraction layer 450 includes a first optical layer 451 and asecond optical layer 452. The first optical layer 451 is disposedbetween the second electrode OE2 and the upper substrate 420 tocorrespond to the second area OA2, and the second optical layer 452 isdisposed between the second electrode OE2 and the upper substrate 420 tocorrespond to the first area OA1.

The light emitted from the organic light emitting device OL travels invarious directions. Among the light emitted from the organic lightemitting device OL, a side surface light SL traveling to the blackmatrix 421 is blocked by the black matrix 421, and then absorbed, sothat the light transmission efficiency of the display panel 400 isreduced. According to the present exemplary embodiment, because thefirst optical layer 451 has relatively large degree of haze, the firstoptical layer 451 scatters the side surface light SL such that thescattered side surface light SL exits to the outside through the uppersubstrate 420 corresponding to the display area DA. As a result, thelight transmission efficiency of the display panel 400 is increased.

The optical path of the side surface light SL having the first set ofcolor coordinates is changed by the first optical layer 451, and theside surface light SL exits to the outside through the upper substrate420 corresponding to the display area DA together with the front surfacelight FL having the second set of color coordinates. Accordingly, thelight obtained by mixing the side surface light SL and the front surfacelight FL, which have different sets of color coordinates, is perceivedby the user. Thus, variations of the color coordinates may be reducedregardless of the viewing angle.

FIG. 10 is a cross-sectional view showing a display panel 403 accordingto another exemplary embodiment of the present invention. In FIG. 10,the same reference numerals denote the same elements in FIGS. 1 to 7,and thus detailed descriptions of the same elements will be omitted.

Referring to FIG. 10, the display panel 403 includes a light extractionlayer 460. The display panel 403 has the same structure and function asthose of the display panel 401 shown in FIG. 6, except for the lightextraction layer 460.

The light extraction layer 460 includes a first optical layer 461 and asecond optical layer 462. The first optical layer 461 and the secondoptical layer 462 are disposed between the second electrode OE2 and theupper substrate 420.

According to the present exemplary embodiment, the first optical layer461 and the second optical layer 462 may be arranged in various shapes.For instance, the first optical layer 461 and the second optical layer462 may be disposed in one of the display area DA and the non-displayarea NDA, and alternately arranged with each other.

The light emitted from the organic light emitting device OL travels invarious directions. Among the light emitted from the organic lightemitting device OL, a side surface light SL traveling to the blackmatrix 421 is blocked and absorbed by the black matrix 421, therebyreducing the light transmission efficiency of the display panel 400.According to the present exemplary embodiment, because the first opticallayer 451 has a relatively large degree of haze, the second opticallayer 462 scatters the side surface light SL to allow the scattered sidesurface light SL to exit to the outside through the upper substrate 420corresponding to the display area DA. As a result, the lighttransmission efficiency of the display panel 400 is increased. Inaddition, the first optical layer 461 and the second optical layer 462are alternately arranged with each other in the display area DA. Thus,the side surface light SL may be effectively extracted by the firstoptical layer 461 and the second optical layer 462.

According to the simulated result, when the light extraction layer 460is present, the light transmission efficiency may be increased by about30% over the case in which the light extraction layer 460 is notpresent.

In addition, the optical path of the side surface light SL having thefirst set of color coordinates is changed by the second optical layer452, and the side surface light SL exits to the outside through theupper substrate 420 corresponding to the display area DA together withthe front surface light FL having the second set of color coordinates.Accordingly, the light obtained by mixing the side surface light SL andthe front surface light FL, which have different sets of colorcoordinates, is perceived by the user. Thus, variations of the colorcoordinates may be reduced regardless of the viewing angle.

In particular, the number of times in which the side surface light SLmeets the second optical layer 462 while traveling along the opticalpath thereof in the display area DA is greater than the number of timesat which the front surface light FL meets the second optical layer 462while traveling along the optical path thereof. Thus, the side surfacelight SL is scattered to a greater degree than the front surface lightFL, Thus, the light transmission efficiency of the display panel 403 isincreased, thereby reducing the variations of the color coordinatesaccording to the viewing angle.

FIG. 11 is a graph showing the simulation result of the color coordinatevariation as a function of the viewing angle of the comparison exampleand the display panel 403 according to an exemplary embodiment of thepresent invention.

Referring to FIG. 11, the variations of the color coordinates on the CIEcoordinate system (Auv) are calculated while changing the viewing anglefrom about zero (0) degrees to about 70 degrees. When the viewing angleis about 70 degrees, the variations of the color coordinates of thedisplay panel 406 in the comparison example are about 0.0282, while thevariations of the color coordinates of the display panel 406 to whichthe light extraction layer 460 is applied are about 0.0146. When thelight extraction layer 460 is applied to the display panel 406, thevariations of the color coordinates are reduced by about 50% compared tothat of the comparison example.

FIGS. 12A to 12E are cross-sectional views showing a method ofmanufacturing a display panel according to an exemplary embodiment ofthe present invention. In FIGS. 12A to 12E, the same reference numeralsdenote the same elements in FIGS. 1 to 5, and thus, detaileddescriptions of the same elements will be omitted. FIGS. 12A to 12E showthe method of manufacturing the display panel 400 shown in FIG. 5.

Referring to FIGS. 12A to 12E, the method of manufacturing the displaypanel includes forming the lower substrate 410, providing the polymernetwork liquid crystal, forming the light extraction layer 430, andforming the upper substrate 420.

FIG. 12A shows the forming of the lower substrate 410. The second gateelectrode GE2 is formed on the lower substrate 410, and the gateinsulating layer GI is formed on the lower substrate 410 to cover thesecond gate electrode GE2. The semiconductor layer AL is formed on thegate insulating layer GI. The second source electrode SE2 and the seconddrain electrode DE2 are formed on the semiconductor layer AL and spacedapart from each other.

The insulating layer 412 is formed on the lower substrate 410. Theinsulating layer 412 covers the second transistor TR2. The display areaDA and the non-display area NDA are defined in the lower substrate 410.The insulating layer 412 is partially etched to form the contact hole inthe non-display area NDA, through which the portion of the second drainelectrode DE2 is exposed.

The first electrode OE1 is formed in the contact hole and the displayarea DA. The pixel definition layer 413 is formed on the insulatinglayer 412 and the first electrode OE1. The pixel definition layer 413 isdisposed to correspond to the non-display area NDA. The pixel definitionlayer 413 has the opening corresponding to the display area DA to exposethe first electrode OE1 through the opening.

The light emitting layer EL is formed on the first electrode OE1 and thepixel definition layer 413 adjacent to the first electrode OE1. Thesecond electrode OE2 is formed over the lower substrate 410. The secondelectrode OE2 covers the pixel definition layer 413 and the lightemitting layer 413.

FIG. 12B shows the providing of the polymer network liquid crystal.

The polymer network liquid crystal PNLC (refer to FIG. 4) is disposed onthe second electrode OE2 to form the polymer network liquid crystallayer PL. The polymer network liquid crystal PNLC may be provided usinga liquid crystal injection method or a liquid crystal dropping method.

FIGS. 12C and 12D show the forming of the light extraction layer 430.

An exposure mask 500 is disposed on the polymer network liquid crystallayer PL. The exposure mask 500 includes a mask substrate 510 and alight blocking portion 520. The mask substrate 510 is formed of atransparent material, e.g., glass.

The first and second areas OA1 and OA2 are defined in the polymernetwork liquid crystal layer PL. The light blocking portion 520 isformed on the mask substrate 510 to correspond to the second area OA2.The light blocking layer 520 is formed of a light blocking material.

The exposure mask 500 is aligned on the polymer network liquid crystallayer PL. When ultraviolet radiation UV is radiated onto the exposuremask 500, the portion of the ultraviolet radiation UV which travels tothe second area OA2 is blocked by the light blocking portion 520. Theother portion of the ultraviolet radiation UV, which travels to thefirst area OA1, is incident to the polymer network liquid crystal layerPL after passing through the exposure mask 500. The polymers PM (referto FIG. 5) are cross-linked to each other in the first area OA1 by theultraviolet radiation UV incident to the polymer network liquid crystallayer PL. Accordingly, the polymer network liquid crystal PNLC in thefirst area OA1 becomes the sheared polymer network liquid crystal S-PNLC(refer to FIG. 5)

The degree of the cross-link of the polymers PM of the polymer networkliquid crystal PNLC is determined depending on the intensity of theultraviolet radiation UV radiated onto the polymer network liquidcrystal PNLC.

The intensity of the ultraviolet radiation UV radiated to the first areaOA1 is not constant. In more detail, the intensity of the ultravioletradiation UV decreases as a distance from the center portion of thefirst area OA1 increases. Therefore, the degree of the cross-link of thepolymer network liquid crystal PNLC in the center portion of the firstarea OA1 is greater than that of the polymer network liquid crystal PNLCin the end portion of the first area OA1 according to the intensity ofthe ultraviolet radiation UV radiated to the first area OA1. Thus, thedistribution of the cross-link of the polymers PM in the polymer networkliquid crystal layer PL of the first area OA1 corresponds to the convexlens structure.

The exposure mask 500 is removed from the polymer network liquid crystallayer PL and the lower substrate 410.

When the forming of the light extraction layer 430 is carried out, thesecond optical layer 432 having the convex lens structure and includingthe sheared polymer network liquid crystal S-PNLC is formed in the firstarea OA1, as shown in FIG. 12D. The first optical layer 431 includingthe polymer network liquid crystal PNLC is also formed to surround thesecond optical layer 432.

FIG. 12E shows the forming of the upper substrate 420.

The color filter 422 is formed on the upper substrate 420 to correspondto the display area DA. The black matrix 421 is formed on the uppersubstrate to correspond to the non-display area NDA. The upper substrate420 faces the lower substrate 410 while being coupled to the lowersubstrate 410 such that the light extraction layer 430 is disposedbetween the lower substrate 410 and the upper substrate 420.

FIGS. 13A and 13B are cross-sectional views showing a method ofmanufacturing a display panel according to another exemplary embodimentof the present invention. In FIGS. 13A and 13B, the same referencenumerals denote the same elements in FIGS. 12A to 12E, and thus,detailed descriptions of the same elements will be omitted.

In the present exemplary embodiment, the method of manufacturing thedisplay panel includes forming the lower substrate 410, providing thepolymer network liquid crystal PL, forming the upper substrate 420, andforming a light extraction layer 430′. The method of manufacturing thedisplay panel is the same as the method of manufacturing the displaypanel described with reference to FIGS. 12A to 12E, except for theforming of the upper substrate 420 and the light extraction layer 430′.

FIGS. 13A and 13B show the forming of the upper substrate 420 and thelight extraction layer 430′.

Referring to FIGS. 13A and 13B, the color filter 422 is formed on theupper substrate 420 to correspond to the display area DA and the blackmatrix 421 is formed to correspond to the non-display area NDA. Theupper substrate 420 faces the lower substrate 410 and is coupled to thelower substrate 410 such that the light extraction layer 430′ isdisposed between the lower substrate 410 and the upper substrate 420.

When the ultraviolet radiation UV is radiated onto the upper substrate420, a portion of the ultraviolet radiation UV, which travels to thenon-display area NDA, is blocked by the black matrix 421. The otherportion of the ultraviolet radiation UV, which travels to the displayarea DA, is incident to the polymer network liquid crystal layer PLafter passing through the upper substrate 420. The polymers PM (refer toFIG. 5) of the polymer network liquid crystal layer PL are cross-linkedto each other in the display area DA by the ultraviolet radiation UVincident to the polymer network liquid crystal layer PL. Accordingly,the polymer network liquid crystal PNLC in the display area DA becomesthe sheared polymer network liquid crystal S-PNLC (refer to FIG. 5). Asdescribed with reference to FIG. 12C, the polymer network liquid crystallayer PL may be exposed to the ultraviolet radiation UV to allow thedistribution of the cross-link of the polymers PM to correspond to theconvex lens structure.

When the forming of the light extraction layer 430′ is carried out, thesecond optical layer 432′ having the convex lens structure and includingthe sheared polymer network liquid crystal S-PNLC is formed in thedisplay area DA, and also the first optical layer 431′ including thepolymer network liquid crystal PNLC is formed to surround the secondoptical layer 432′.

As described above, the black matrix 421 blocks the ultraviolet ray UVas the exposure mask 500 (refer to FIG. 12C). Thus, the light extractionlayer 430′ may be formed without using the exposure mask 500.

FIGS. 14A to 14C are cross-sectional views showing portions of a methodof manufacturing a display panel according to another exemplaryembodiment of the present disclosure. In FIGS. 14A to 14C, the samereference numerals denote the same elements in FIGS. 12A to 12E, andthus detailed descriptions of the same elements will be omitted.

The method of manufacturing the display panel includes forming the lowersubstrate 410, providing the polymer network liquid crystal layer PL,forming a light extraction layer 460, and forming the upper substrate420. The method of manufacturing the display panel shown in FIGS. 14A to14C is the same as the method of manufacturing the display panel shownin FIGS. 12A to 12E, except for the forming of the light extractionlayer 460 and the upper substrate 420.

An alignment substrate 600 is formed on the polymer network liquidcrystal layer PL. The alignment substrate 600 includes a transparentsubstrate 610 and the alignment electrode 620. The transparent substrate610 includes the transparent material, e.g., glass.

The first and second areas OA1 and OA2 are defined in the polymernetwork liquid crystal PL. The first and second areas OA1 and OA2 arealternately arranged with each other in the first direction D1, and aplurality of the first and second areas OA1 and OA2 is provided. In moredetail, the first optical layer 460 and the second optical layer 462 arealternately arranged in the display area DA and the non-display areaNDA.

The alignment electrode 620 is disposed on the transparent substrate 610to correspond to the first area OA1. The alignment electrode 620 may be,for example, a transparent electrode, e.g., indium tin oxide, and isaligned on the polymer network liquid crystal layer PL.

A first voltage is applied to the alignment electrode 620, and a secondvoltage is applied to the opposite electrode, which is disposed to facethe alignment electrode 620 while the polymer network liquid crystallayer PL is disposed between the alignment electrode 620 and theopposite electrode. In the present exemplary embodiment, the oppositeelectrode may be the second electrode OE2. When the first and secondvoltages are applied to the alignment electrode 620 and the secondelectrode OE2, respectively, an electric field corresponding to thedifference between the first and second voltages is formed in adirection substantially parallel to the third direction D3, whilecrossing the polymer network liquid crystal layer PL in the first areaOA1.

The polymers PM (refer to FIG. 7) and the liquid crystals LM in thefirst area OA1 are aligned in the third direction D3 in response to theelectric field.

When the ultraviolet radiation UV is radiated onto the alignmentsubstrate 600, the ultraviolet radiation UV is incident to the polymernetwork liquid crystal layer PL after passing through the alignmentsubstrate 600. The polymers PM of the polymer network liquid crystallayers PL in the first area OA1 are cross-linked to each other by theportion of the ultraviolet radiation UV that is incident to the firstarea OA. Accordingly, the sheared polymer network liquid crystal S-PNLC(refer to FIG. 7) is formed in the first area OA1.

The polymers PM of the polymer network liquid crystal layer PL in thesecond area OA2 are cross-linked to each other by the ultravioletradiation UV incident to the second area OA2. Therefore, the alignedpolymer network liquid crystal O-PNLC is formed in the second area OA2.

When the forming of the light extraction layer 460 is carried out, thefirst optical layer 461 including the aligned polymer network liquidcrystal O-PNLC is formed in the first area OA1, and the second opticallayer 462, including the sheared polymer network liquid crystal S-PNLC,is formed in the second area OA2.

The alignment substrate 600 is then removed from the polymer networkliquid crystal layer PL and the lower substrate 410, as shown in FIG.14B.

The color filter 422 is formed on the upper substrate 420 to correspondto the display area DA and the black matrix 421 is formed to correspondto the non-display area NDA. The upper substrate 420 faces the lowersubstrate 410, and is coupled to the lower substrate 410 such that theliquid extraction layer 460 is disposed between the lower substrate 410and the upper substrate 420.

FIGS. 15A and 15B are cross-sectional views showing a method ofmanufacturing a display panel according to another exemplary embodimentof the present disclosure. In FIGS. 15A and 15B, the same referencenumerals denote the same elements in FIGS. 14A to 14C, and thus,detailed descriptions of the same elements will be omitted.

In the present exemplary embodiment, the method of manufacturing thedisplay panel includes forming the lower substrate 410, providing thepolymer network liquid crystal layer PL, forming the upper substrate420, and forming of the light extraction layer 460′. The method ofmanufacturing the display panel is the same as the method ofmanufacturing the display panel described with reference to FIGS. 14A to14C, except for the forming of the upper substrate 420 and the lightextraction layer 460′.

The color filter 422 is formed on the upper substrate 420 to correspondto the display area DA, and the black matrix 421 is formed to correspondto the non-display area NDA. The upper substrate 420 faces the lowersubstrate 410 and is coupled to the lower substrate 410, and the lightextraction layer 460′ is disposed between the lower substrate 410 andthe upper substrate 420.

The first area OA1 and second area OA2 are defined in the display areaDA of the polymer network liquid crystal layer PL. The first area OA1and second area OA2 are alternately arranged in the first direction D1,and a plurality of the first areas OA1 and a plurality of the secondareas OA2 are provided.

The alignment electrode 620′ is disposed to correspond to the first areaOA1.

When the first and second voltages are respectively applied to thealignment electrode 620′ and the second electrode OE2, the polymers PMand the liquid crystals LM in the first area OA1 are aligned in thethird direction D3 in response to the electric field.

The ultraviolet radiation UV is radiated onto the alignment substrate600. Accordingly, the polymer network liquid crystal PNLC of the firstarea OA1 becomes the sheared polymer network liquid crystal S-PNLC, andthe polymer network liquid crystal PNLC of the second area OA2 becomesthe aligned polymer network liquid crystal O-PNLC.

When the forming of the light extraction layer 460′ is carried out, thefirst optical layer 461′, including the aligned polymer network liquidcrystal O-PNLC, is formed in the first area OA1, and the second opticallayer 462′, including the sheared polymer network liquid crystal S-PNLC,is formed in the second area OA2.

Similar to the alignment electrode 620 (refer to FIG. 14A), thealignment electrode 620′ aligns the polymers PM (refer to FIG. 7) andthe liquid crystals LM (refer to FIG. 7). Therefore, the lightextraction layer 460′ may be formed without using the alignmentsubstrate 600 (refer to FIG. 14A).

According to the above, the light extraction layer allows light emittedfrom the organic light emitting device to exit to the outside of theorganic light emitting diode display panel through the first and secondoptical layers, each of which having different optical properties.Therefore, the light transmission efficiency of the organic lightemitting diode display panel is increased. In addition, the opticalproperties of the first and second optical layers are controlled byprocessing the polymer network liquid crystal. Thus, the lightextraction layer may be easily formed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of manufacturing an organic lightemitting diode display panel, comprising: forming a lower substrate, thelower substrate comprising a first area and a second area; forming anorganic light emitting device on the lower substrate; disposing apolymer network liquid crystal on the organic light emitting device;forming a second optical layer in the second area, the second opticallayer comprising the polymer network liquid crystal; and varying anoptical property of the polymer network liquid crystal so as to form afirst optical layer in the first area.
 2. The method of claim 1, whereinthe forming of the first optical layer comprises curing the polymernetwork liquid crystal of the first area to form a sheared polymernetwork liquid crystal.
 3. The method of claim 2, wherein the curing ofthe polymer network liquid crystal comprises radiating ultraviolet lightto the polymer network liquid crystal of the first area.
 4. The methodof claim 3, wherein the radiating of the ultraviolet light comprisesshadow masking the second area.
 5. The method of claim 4, furthercomprising disposing an upper substrate on the polymer network liquidcrystal, the upper substrate comprising a black matrix facing the secondarea, wherein the shadow masking of the second area is performed usingthe black matrix.
 6. The method of claim 4, wherein the shadow maskingof the second area comprises: aligning an exposure mask comprising thelight blocking material on the polymer network liquid crystal to facethe second area; exposing the polymer network liquid crystal using theexposure mask; and removing the exposure mask.
 7. The method of claim 4,wherein an intensity of the ultraviolet light decreases as a distancefrom a center portion of the first area increases.
 8. The method ofclaim 1, wherein the forming of the first optical layer comprisesforming an aligned polymer network liquid crystal in the first area, theforming of the aligned polymer network liquid crystal comprising:applying an electric field to the polymer network liquid crystal facingthe first area; and radiating the ultraviolet light onto at least thefirst area.
 9. The method of claim 8, further comprising forming anopposite electrode under the polymer network liquid crystal, wherein theapplying of the electric field comprises: aligning an alignmentsubstrate comprising an alignment electrode opposing the oppositeelectrode on the polymer network liquid crystal; and applying voltagesto the alignment electrode and the opposite electrode, respectively, toapply the electric field to the polymer network liquid crystal.
 10. Themethod of claim 9, further comprising: removing the alignment substrate;and disposing the upper substrate on the first and second opticallayers.
 11. The method of claim 8, further comprising: forming anopposite electrode under the polymer network liquid crystal; forming anupper substrate comprising an alignment electrode facing the oppositeelectrode; and disposing the upper substrate on the polymer networkliquid crystal, wherein the applying of the electric field comprisesapplying voltages to the alignment electrode and the opposite electrode,respectively, to apply the electric field to the polymer network liquidcrystal.